func getRIndex(strs []string, str string) int {
	for i := len(strs) - 1; i >= 0; i-- {
		if strs[i] == str {
			return i
		}
	}
	return -1
}

func sortCallbacks(cs []*callback) (fns []func(*DB), err error) {
	var (
		names, sorted []string
		sortCallback  func(*callback) error
	)
	sort.SliceStable(cs, func(i, j int) bool {
		if cs[j].before == "*" && cs[i].before != "*" {
			return true
		}